artlets class absences

hello! upcoming freshie here from arts and letters. ask ko lang how many allowed absences exactly is meant by 20% per term? i'm gonna be going on a trip kasi so i'll be absent ng Aug 18-22 (minus the 21st kasi holiday naman.) So bali sa official week of class proper sya. Then ask ko na rin how is the process here like do I pass or email an excuse letter? and to who? huhu